1. Field of the Invention
The present invention relates to an inkjet printing apparatus that ejects ink to perform a printing operation and an inkjet printing head used for the printing apparatus.
2. Description of the Related Art
Conventionally, the inkjet printing apparatus achieves a reduced running cost for color images and also can have a smaller size. Thus, the inkjet printing apparatus has been widely used for computer-related output devices and has been commercialized.
In recent years, in order to realize the printing of high-definition images with a higher speed, a printing head having a wider printing width (or an ejection opening array having a longer length) also has been desired. Specifically, a printing head having a length of 4 inches to 13 inches also has been required.
The printing head having a longer length and a higher speed as described above causes an increased energy inputted to the printing head to consequently cause an increased temperature rise of the printing head during a printing operation. This consequently requires measures for preventing factors deteriorating the printing reliability (e.g., fluctuation in the ejection amount for the respective pages, unstable ejection at a high temperature, a deteriorated continuous printing operation).
Conventionally, the printing head has been cooled by methods such as air cooling from the outside of the printing head or a cooling pipe attached to the printing head.
In the conventional method, the completed printing head is externally attached with a heat pipe or a radiation member. Thus, a disadvantage has been caused where a printing element substrate as a heat source cannot be provided in the close vicinity of the heat pipe. The externally-attached heat pipe also causes a limited area at which the heat pipe contacts with the printing head, thus causing a poor heat transfer efficiency between the printing head and the heat pipe. Some conditions for executing the printing operation may provide, even in the conventional configuration, sufficient cooling and soaking effects. However, the conventional configuration is disadvantageous when the printing head having a longer length and a higher density is used to continuously perform a printing operation for a longer time. This is due to that the conventional configuration cannot provide a heat transfer efficiency enough to suppress a defective printing due to an uneven temperature distribution and a temperature rise in the printing head due to the long-time printing.